JPH0648549A - Longitudial tear detector of conveyer belt - Google Patents

Abstract

PURPOSE:To provide a longitudinal tear detector of conveyer belt for accurately detecting the longitudinal tearing of the belt even when the distance between a sensor for detecting the status of a material to be detected, which is embedded in the belt, and a controller for judging the longitudinal tearing gets longer. CONSTITUTION:The disconnected status of a coil C embedded in a plurality of points of a conveyer belt 3, is detected by a sensor 5 externally provided. A V/F converter 9 for converting the voltage signal issued from the sensor into frequency, is provided in a transmission box 8 in the vicinity of the sensor 5, while an F/V converter 11 for re-converting the frequency into the voltage signal is provided in a control box 10, and the V/F converter 9 and the F/V converter 11 are connected together by a signal cable 13, while a pulse generator 6 for detecting the amount of rotation of a following pulley 2 and the control box 10 are connected together by a signal cable 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for automatically detecting vertical tears generated on a conveyor belt during operation of the conveyor.

[0002]

2. Description of the Related Art When a moving conveyor belt is pierced by, for example, a sharp metal piece, it acts like a knife and tears the belt in the traveling direction (longitudinal direction). There is. Even with a steel cord conveyor belt, the cord is embedded in the lengthwise direction of the belt, and therefore does not help prevent vertical tearing.

In order to prevent such vertical tearing over a long distance, the objects to be detected such as loop coils and resonant circuits are embedded in the belt at a plurality of positions at intervals in the running direction, and the state of the objects to be detected is detected by a sensor. The method of detecting is generally used. The sensor is installed at an external fixed position near the running path of the belt, and detects a signal from each detected object passing through this installation point and sends it to the control device. When a vertical tear occurs, the sensor does not detect the signal and does not transmit the signal because the detected object is broken, so the control device determines that "vertical tear has occurred" and stops the running of the belt. In this way, vertical tearing is minimized and the belt can be reused with minor repairs. Techniques for detecting such a vertical tear are disclosed in, for example, Japanese Patent Laid-Open Nos. 3-26603, 3-297719, and 3-58460.
Therefore, in order to facilitate understanding of the present invention, as a representative example, the one disclosed in Japanese Patent Laid-Open No. 3-26603 will be described with reference to FIG.

In the conveyor apparatus shown in FIG. 2 (a), a steel cord conveyor belt 3 is wound between a drive pulley 1 and a driven pulley 2 and conveys a substance supplied from a chute 4. Inside the belt 3, loop coils C (C ₀ , C ₁ , C ₂ , C ₃ , C ₄ ,
(...) is buried. As shown in FIG. 2B, each coil C has a rectangular closed loop whose long side extends over almost the entire width of the belt 3 and is formed of a conductive wire, and is a low-strength wire that is always broken when the belt 3 is vertically torn. In addition, it is formed using a conductive wire that is unlikely to be broken due to bending fatigue. It should be noted that, of the two coils that are extremely close to each other, one coil C ₀ is a reference coil for calculating the belt traveling distance, and the other coil is C _1, and hereinafter the direction opposite to the belt traveling direction is set. A coil of C ₂ or less is embedded in the. As shown in FIG. 1A, the vertical tear detection control system includes a sensor 5 installed near the lower surface of the belt 3, a pulse generator 6 attached to the rotary shaft of the driven pulley 2, and a control device 7.
Consists of. The configuration and function of the main part will be briefly described below.

(1) Sensor 5 The sensor 5 is shown in FIG.
As shown in FIG. 2, a combination of the high frequency transmitter 5a and the receiver 5b is used. If the coil C that has reached the installation point of the sensor 5 is not broken as the belt 3 runs, the high frequency from the transmitter 5a causes the coil C to move. An induced current flows through the detector, which is detected by the receiver 5b. In this way, the sensor 5 can detect the normal state of the coil C passing through the installation point (that is, the belt has no vertical tear). (2) Pulse generator 6 The pulse generator 6 emits a pulse signal according to the rotation amount of the driven pulley 2. Driven pulley 2
Since the rotation amount and the traveling distance of the belt 3 substantially correspond to each other except for an error due to a slip between the two, the number of pulses generated by this indicates the traveling distance of the belt 3. (3) Control device 7 The control device 7 stores the number of pulses input from the pulse generator 6 and the like.
The presence or absence of vertical tearing is determined by processing the signal from the sensor and the signal from the sensor 5 according to a predetermined step, and when it is determined that the vertical tearing has occurred, the conveyor is stopped or an alarm is issued. FIG. 3 illustrates an example of a method of detecting the occurrence of the vertical tear. That is, when the start coil C ₀ and the vertical tear detection coil C ₁ arrive at the sensor, the vertical tear detection coils (C _{2 to} C _n ) that arrive thereafter are detected.
When the start coil C ₀ and the vertical splitting detection coil C ₁ arrive at the sensor again, the detection is started (see FIG. 3 (a)). Then, as shown in FIG. 3 (b), when a vertical tear occurs in the belt, that portion (T)
No signal is emitted even when the sensor arrives at the sensor, so a belt stop signal is output from the control device.

The one disclosed in Japanese Unexamined Patent Publication No. 3-297719 is a double-closed rectangular closed loop coil disclosed in Japanese Unexamined Patent Publication No. 3-26603, and is disclosed in Japanese Patent Publication No. 3-58460. The one that is wound is a coil wound in an annular shape, all of which prevent the coil from breaking due to bending fatigue other than vertical tearing, and can improve the detection accuracy when a true vertical tear occurs. .

By the way, the distance between the signal cable connecting the sensor and the control device in the actual machine is often 50 m or more. Then, when the distance of the signal cable is increased in this way, the output signal of the sensor is weakened by the attenuation of the resistance of the signal cable itself and the noise jump, so that a clear signal (for example, a signal having an S / N ratio of 3: 1 or more) is used. ) Is difficult to obtain. Therefore, the control device itself has the ability to process signals from a plurality of sensors, but the received signal becomes weaker as the distance of the signal cable becomes longer, which makes it impossible to accurately determine the vertical tear. Therefore, in the conventional vertical tear detection technology disclosed in the above publications, the detection sensor 1
One controller was required for each.

The present invention has been made in view of the above problems of the prior art, and an object thereof is a sensor for detecting the state of an object to be detected embedded in a belt and a control for determining vertical tearing. An object of the present invention is to provide a conveyor belt vertical tear detection device capable of accurately detecting the belt vertical tear even if the distance to the device is long.

[0009]

In order to achieve the above object, the gist of the present invention is to detect the normal state or disconnection state of an object to be detected embedded in a plurality of places of a conveyor belt with an externally installed sensor, In a device for detecting the occurrence of vertical tearing of the belt by subjecting a voltage signal emitted from the sensor to a predetermined process by a control device, V / which converts the voltage signal emitted from the sensor into a frequency in the vicinity of the sensor.
An F converter is arranged, and an F / V converter for converting the frequency into a voltage signal is arranged again in the control device.
A vertical tear detection device for a conveyor belt is characterized in that the / F converter and the F / V converter are connected by a signal cable.

[0010]

The voltage signal emitted from the sensor is an analog quantity, but it is converted into a digital pulse train or a rectangular wave having a frequency exactly proportional to the analog quantity by the V / F converter, and a fixed distance is passed through the signal cable. Reach a remote control unit. Then, it is converted again into an analog voltage by the F / V converter, and the presence / absence of a vertical tear is detected through a predetermined process. When a vertical tear occurs, a signal for stopping the operation of the conveyor belt is output from the control device, and a predetermined repair work is performed.

[0011]

Embodiments of the present invention will be described below with reference to FIG. In FIG. 1, reference numerals 1 to 6 are the same as those in FIG. 2, and the loop coils C (C ₀ , C ₁ , C ₂ , C ₃ , C ₄ , ...
., C _n ) are buried. 8 is a V / F converter 9
Is a control box having an F / V converter 11, and 12 is a control panel for instructing stop / start of the drive motor of the drive pulley 1 by the output from the control box 10. The V / F converter 9 and the F / V converter 11 are connected by a signal cable 13, and the pulse generator 6 and the control box 10 are connected by a signal cable 14. An example of how to use the conveyor belt vertical tear detection device having such a configuration will be briefly described below.

(1) Storing the interval of the coil C First, in order to store the interval of each coil, the conveyor device is operated. Then, the two coils C detected by the sensor 5 almost at the same time are designated as C ₀ · C _1, and each time a detection signal is subsequently input, they are numbered as C ₂ , C ₃ , C ₄ , ..., C _n. At the same time, the number of pulses input from the pulse generator 6 to the control box 10 via the signal cable 14 between the detection signals is calculated as, for example, p ₁ , p ₂ , p ₃ , p ₄ ,
, _Pn are stored as the intervals between the coils C. Then, when the belt 3 goes around once and the above-mentioned coils C ₀ and C ₁ are detected again, the vertical tear detection is started.

(2) Detection of vertical tearing The coil C (for example, coil C) detected by the sensor 5 is detected.
_k : k = 1 to n) is detected by the V / F converter 9,
When it is transmitted to the F / V converter 11 in the control box 10 via the signal cable 13, the belt 3
It is determined that no vertical tear has occurred. Then, by counting the number of pulses h _k to the current after the detection signal is compared corresponds to the number of pulses p _k stored as a coil arrangement portion corresponding to the number of pulses h _k, p _k-.alpha. ≦ h _k ≤
When it enters the range of p _k + α (α is an allowable constant in consideration of elongation and slip of the belt 3), it waits for a signal from the sensor 5. Here, if there is a detection signal from the sensor 5,
It is determined that the vertical tear has not occurred at the position of the coil C _{k + 1} following the previous coil C _k , and the counting of the next pulse number h _{k + 1} is started.

If the belt 3 is vertically torn, it means that the coil of the corresponding portion is broken, and the sensor 5
Since the signal from does not reach the control box 10, the count of the pulse number h _k progresses, and when h _k > _pk + α, it is determined that the vertical split has occurred in the coil C _{k + 1} , and the control box 10 A signal is issued to the control board 12 to stop the drive pulley 1.

(3) Measures for occurrence of vertical tearing When the conveyor apparatus is stopped as described above, the operator can check the appearance of the belt 3 centering around the buried portion of the corresponding coil C (C _{k + 1} in this embodiment). After checking and taking the prescribed measures, restart the operation. Thereafter, the vertical tear detection is performed by counting the number of pulses and determining the presence / absence of a detection signal by the same method.

In the above embodiment, the case where the number of sensors is one and the number of control boxes is also one is shown, but the signals from a plurality of sensors (a plurality of pulse generators and a plurality of transmission boxes) are used as one control box. It is also possible to judge the processing by. Although the pulse generator also generates an analog voltage, the voltage is generally high (maximum DC 24 V), and the decrease in S / N ratio due to signal attenuation is negligible.
No auxiliary means for signal transmission such as a transmission box is required. Further, an amplifier can be provided between the V / F converter and the F / V converter. The reliability of the transmitted signal is further improved by providing such an amplifier.

[0017]

Since the vertical tear detection device for a conveyor belt according to the present invention is configured as described above, it has the following effects. (1) The sensor signal is transmitted to the control box without being attenuated even when the signal cable is extended over a long distance, and is not affected by noise, so that stable vertical crack detection can be performed reliably. (2) It is possible to process the signals from multiple sensors with one control box, and it is not necessary to have the same number of control boxes as the number of sensors as in the conventional system. In the case of concentrated detection, the equipment cost can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a vertical tear detection device for a conveyor belt according to the present invention.

FIG. 2 (a) is a configuration diagram of a conventional conveyor belt vertical tear detection device, and FIG. 2 (b) is a view taken along the line II-II of FIG. 2 (a).

3 (a) and 3 (b) are pulse waveform and signal charts for explaining the vertical tear detection method.

[Explanation of symbols]

 1 ... Drive pulley 2 ... Following pulley 3 ... Steel cord conveyor belt 4 ... Chute 5 ... Sensor 6 ... Pulse generator 7 ... Control device 8 ... Transmission box 9 ... V / F converter 10 ... Control box 11 ... F / V converter 12 … Control panel 13, 14… Signal cable

Claims (1)

[Claims] 1. An externally installed sensor detects a normal state or a disconnection state of an object to be detected embedded in a plurality of portions of a conveyor belt, and a control device performs a predetermined process on a voltage signal generated from the sensor. In the device for detecting the occurrence of vertical tearing of the belt, a V / F converter for converting a voltage signal emitted from the sensor into a frequency is arranged in the vicinity of the sensor, and an F / F converter for converting the frequency into a voltage signal again is provided.
/ V converter is arranged in the above-mentioned control device, and these V / F
A vertical tear detection device for a conveyor belt, wherein the converter and the F / V converter are connected by a signal cable.